Climate change significantly impacts wetlands, which serve as carbon sinks and support livelihoods. Madhubani, being one of the rainiest districts of Bihar, has more than 2% of its geographical area under wetlands. High rainfall variability poses a threat to wetland sustainability. This paper is an attempt to identify how the variability of rainfall affects the wetland ecosystem’s sustainability in Madhubani. Through an analysis of the patterns and fluctuations in seasonal and yearly precipitation since the twentieth century, the study attempts to establish how the spatial extent and wetness of wetlands have declined due to changes in hydrological dynamics. The observed significant decline in annual rainfall and highly variable seasonal rainfall points toward emerging long dry spells and drought conditions over Madhubani, especially during the last two decades. The analysis of hydrological changes in Madhubani’s wetlands highlights shifting wetness patterns during pre-monsoon and post-monsoon periods, reflecting the broader impacts of climate change. Autoregressive Integrated Moving Average (ARIMA) model projections, highlighting future climate risks, indicate a continued decline in rainfall, posing challenges to biodiversity, livelihoods, and economic stability, thereby complicating sustainable adaptation efforts.